Using the Caterpillar vehicle's front-mounted shovel, the driver repeatedly rammed a bus full of passengers until it flipped over. One woman was killed instantly when the shovel pierced the windshield of her car.

Israeli radio reporter Yitzhak Noy witnessed part of the attack and said he briefly made eye contact with the driver. He was, Noy said, "a young, handsome man. He looked cold and focused."

Israeli police identified the assailant as Hussam Dwayat, a 30-year-old father of two from Sour Baher, an Arab village on the southern outskirts of Jerusalem. Security forces quickly descended on the family home and questioned several of his relatives but made no arrests.

Dwayat normally drove the front-loader as part of a construction project to install a commuter rail system in Jerusalem.

But just before noon, Dwayat apparently came to the construction site and commandeered the vehicle. Rosenfeld speculated that his ultimate target was a crowded open-air market a few hundred yards from where the attacker was killed.

The attack took place on Jaffa Road, one of downtown Jerusalem's main east-west corridors. But the light-rail construction has closed several lanes, which made it difficult for cars to escape the rampaging vehicle and later hindered the arrival of ambulances and rescue vehicles.

Survivor Miki Aronson was turning off Jaffa Road into a parking lot and thought the oncoming construction vehicle was signaling to let her pass.

"But then he just came at me. He kept coming at me, crushing over the car," Aronson told Israeli radio. "He crushed it like a box. I have no idea how I am alive now."

Rosenfeld, the police spokesman, said Dwayat appeared to have acted alone, although several obscure Palestinian militant groups issued conflicting claims of responsibility.

The attack was the first in Jerusalem since early March, when a Palestinian gunman from East Jerusalem killed eight young students inside a seminary.

"Jerusalem is a complex city, where Arabs and Jews have lived together for tens, even hundreds of years," Police Commissioner Dudi Cohen said. "The security and public reality is a complex one."

Residents of Sour Baher described Dwayat as an unassuming and apolitical family man. One neighbor, who did not wish to be identified, said the Dwayat family has been warned by Israeli officials not to erect a traditional mourning tent to honor him. Many Israelis were enraged in March when the family of Alaa Abu Dheim, the seminary attacker, erected a mourning tent that included the flag of the militant group Hamas.

After that shooting, several government officials called for the destruction of the Abu Dheim family home. On Wednesday, Lupolianski, the Jerusalem mayor, called for similar treatment for Dwayat's home.

"Any house from which a terrorist came must be demolished, without a doubt," he said.

Dwayat had been fined $50,000 for building his house without a permit, and a demolition order was on file, said Hassib Nashashibi, head of a group that defends Palestinians against such orders, The Associated Press reported.